Test-positive rate at CT colonography is increased by rectal bleeding and/orunexplained weight loss, unlike other common gastrointestinal symptoms

Purpose: We evaluated the rate of significant colonic and extra-colonic abnormalities at computed tomography colonography (CTC), accordingto symptoms and age.
Materials and methods: We retrospectively evaluated 7361 consecutive average-risk subjects (3073 males, average age: 60.3 ± 13.9; range 18–96years) for colorectal cancer (CRC) who underwent CTC. They were divided into three groups according to clinical symptoms: 1343 asymptomaticindividuals (group A), 899 patients with at least one “alarm” symptom for CRC, including rectal bleeding and unexplained weight loss (groupC), and 5119 subjects with other gastrointestinal symptoms (group B). Diagnostic and test-positive rates of CTC were established using opticalcolonoscopy (OC) and/or surgery as reference standard. In addition, clinically significant extra-colonic findings were noted.
Results: 903 out of 7361 (12%, 95% confidence interval (CI) 0.11–0.13) subjects had at least one clinically significant colonic finding at CTC. CTCtrue positive fraction and false positive fraction were respectively 637/642 (99.2%, 95%CI 0.98–0.99) and 55/692 (7.95%, 95%CI 0.05–0.09). Thepooled test-positive rate in group C (138/689, 20.0%, 95%CI 0.17–0.23) was significantly higher than in both groups A (79/1343, 5.9%, 95%CI0.04–0.07) and B (420/5329, 7.5%, 95%CI 0.07–0.08) (p < 0.001). Aging and male gender were associated to a higher test positive rate. The rateof clinically significant extra-colonic findings was significantly higher in group C (44/689, 6.4%, 95%CI 0.04–0.08) versus groups A (26/1343,1.9%, 95%CI 0.01–0.02) and B (64/5329, 1.2%, 95%CI 0.01–0.02) (p < 0.001).Conclusion: Both test-positive and significant extra-colonic finding rates at CTC are significantly increased in the presence of “alarm” gastroin-testinal symptoms especially in older patients.